Known fire suppression systems used in hoods placed over cook-stoves or ranges are mainly concerned with delivering fire retardant onto the cooking surface to stop fat or grease fires when a temperature indicative of a fire is measured in the hood plenum or ductwork. The existing fire suppression systems operate by measuring a fixed absolute temperature in the hood plenum or the ductwork and either activating an alarm or the release of fire retardant when a previously set temperature has been reached. This type of approach, however, does not account for changes in the exhaust temperature, nor does it account for scenarios where there is only a flare-up from regular cooking, instead of a fire.